48-million-year-old food webs show modern structure

In the most compelling evidence to date that ancient food webs were organised much like modern food webs, researchers have pieced together a highly detailed picture of feeding relationships among 700 mammal, bird, reptile, fish, insect and plant species from a 48 million year old lake and forest ecosystem.

The researchers from the Santa Fe Institute (SFI) and the Smithsonian Institution here compiled data about more than 6,500 feeding relationships among fossilised remains from the Messel deposit near Frankfurt, Germany.

"What we found is that the Messel lake food web looks very much like a modern food web," said professor Jennifer Dunne from SFI.

This is despite the fact that 48 million years of species turnover and evolution separate the Messel lake ecosystem from modern ecosystems.

To understand this, the researchers constructed two networks of feeding interactions - one for the lake and one for the surrounding forest.

Next, they mathematically compared each food web's structural features with those of modern-day food web datasets - matching up such indicators as fractions of cannibals, herbivores and omnivores, the distributions of generalist and specialist feeders, the mean lengths of feeding chains and so on.

"We do not yet have examples of comprehensive modern terrestrial food web datasets that have the high resolution of plants, insects and their interactions that we included in the Messel forest dataset," Dunne noted.

"We want our data to serve as a challenge to ecologists to compile more highly and evenly resolved food web data for extant systems," she said.

Ancient food webs are particularly difficult to reconstruct because data about them is usually limited and of low quality.

But the Messel shale deposit is unique.

Scientists hypothesise that releases of toxic volcanic gases rendered the area's air and water lethal to most life in a short time.

Animals in and near the lake were overwhelmed, and, along with plants, sunk to the low-oxygen depths of the lake where they were smothered in mud and fossilised, soft tissue and all, said a paper published in the journal Proceedings of the Royal Society B.